This invention relates to improved hydro-ski type water borne craft in which lift is attained at high speed by a planing action of the craft along the surface of a body of water.
When a boat having a planing hull reaches a relatively high speed in traveling over the surface of the water, it becomes highly susceptible to overturning or damage by the action of waves which may be present on the water surface. The higher the speed, the greater the danger involved in contact with even very small waves which at slow speeds would be negligible and unnoticed. In order to reduce this adverse effect at high speed, and to attain an increased percentage of load alleviation at such speeds, boats have been designed in which skis movably carried by the hull of the craft have been adjustable upwardly and downwardly relative to the hull in a relationship controllably varying the total amount of planing surface which is properly positioned for contact with the water at different speeds. One such arrangement is shown in U.S. Pat. No. 3,308,780 issued Mar. 14, 1967.
In the type of boat shown in that patent, two skis at opposite sides of a hull coact with a planing undersurface of the hull to support the boat when the skis are in upwardly retracted positions, but act to support the boat independently of any contact of the hull surface with water when the skis are actuated downwardly to high speed extended positions. Thus, the area of contact with the water is greatly reduced at high speeds, and the resultant disruptive effect which can be produced by a wave of a particular size is similarly decreased.
One problem which is encountered in hydro-ski craft is that of maintaining lateral stability of the boat in a relation preventing and counteracting roll movements and maintaining a properly horizontal orientation of the craft. In the arrangements of U.S. Pat. No. 3,149,600 maintenance of lateral stability is attained by controlled manipulation of vectored jets which drive the craft. These vectored jets, however, require undue complexity of construction and actuation, and are difficult for a person to control without a considerable amount of special training. The problem of instability against roll has been even more critical in craft of the "mono-ski" type in which at high speed only a single planing surface, rather than two such surfaces, contacts and planes along the water.